1. Field of the Invention
The present invention relates to a medical probe for accessing the interior of a volume defined by a puncturable material, and more particularly to a needle-type probe insertable through a patient's skin.
2. Description of the Related Art
Prior art needle probes are used, for instance in human medicine, for the direct venipuncture of arterio-venous fistulas, or for venipuncture of fairly large blood vessels for intermittent chronic hemodialysis or for extraction of fairly large quantities of blood from a patient.
Such needles are described in German Pat. Nos. 22 59 865 and 22 59 866. These prior art needles have a sharp, smooth cutting edge for the percutaneous puncture of blood vessels where a traumatism of the skin tissue of the patient is largely suppressed. The cutting edge of these needles creates an arcuate incision in the patient's skin which creates a skin flap defined by the parimeter of the arcuate incision. In order to insert the prior art needles through the patient's skin, a greater pressure must be applied to the patient's skin to create the initial incision than is necessary to insert the needle into the blood vessel below the skin. This higher pressure during initial incision of the needle causes discomfort and pain for the patient. These prior art venipuncture type needles have a large lumen diameter in relation to the needle wall thickness, since up to 300 mililiters of blood per minute at rates up to 4 meters per second must be passed through the needle lumen.
These prior art needles have an open, oblique ground edge acting as a cutting surface and as a rule, a small opening immediately rearward of the puncturing tip which serves to equalize pressure on the inner and outer surfaces of the needle aperture when inserted in a patient's blood vessel. This equalization of pressure acts to prevent the wall of the blood vessel from being sucked onto the ground edge opening and preventing flow through the aperture into the lumen of the needle. However, the necessity for providing the opening increases the cost of manufacture of the needle.
With these prior art needles, patients are subjected to venipuncture for the purpose of hemodialysis more than one hundred times per year, thus requiring numerous incisions to be made through a small area of the patient's skin since only relatively small blood vessels are available for the hemodialysis. As discussed above, upon puncturing of the patient's skin with the prior art needles an arcuate cut is created. It frequently happens that the skin flap formed by the periphery of the arcuate cut is picked up during puncture by the upper edge of the needle opposite the ground edge cutting surface and is drawn into the cut. This results in scarring of the skin tissue where the incision is made. The subsequent healing of the scarred skin tissue results in a thickening of that area of the skin thus impeding a further puncture into that tissue zone. Moreover, the arcuate cut formed in the patient's skin by the incision of the needle does not allow for a tight fit of the skin around the needle shank as the needle is inserted into the patient's body The resulting loose fit of the patient's skin around the needle shank allows for seepage of the blood through the arcuate incision around the needle shank.
The prior art needles described above normally include a holder for a technician to guide the needle onto the patient's skin and blood vessel without obstructing the view onto the puncture point. The needle is normally rotatably mounted in this holder. Unfortunately, during puncture of the patient's skin, it frequently happens that the needle is unintentionally rotated in the holder and thus causes traumatisms to the patient's skin at the insertion point into the blood vessel since the ground edge cutting surface is not properly oriented. Moreover, improper orientation of the needle impedes the flow of blood into the needle lumen.
It is therefore an object of the present invention to provide a probe for insertion through a patient's skin which creates a reduced length of the incision line thus reducing the required pressure on the probe to puncture the patient's skin and reducing the amount of discomfort and pain felt by the patient during insertion.
It is a further object of the present invention to provide a probe for incision through a patient's skin which utilizes the natural elasticity of human skin to stretch the skin around the incision parameter about the periphery of the probe shank thus creating a tight fit of the skin around the shank and eliminating seepage of blood through the incision.
It is a further object of the present invention to provide a holder for a needle probe which selectively restricts rotational movement of the probe when inserted in a patient's body.
It is still a further object of the present invention to provide a method of manufacturing the needle probe of the instant invention.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.